The present invention relates to cutter tools for trimming liners that are inserted into a cylinder bore.
It is desirable to provide sleeve-type inserts (sometimes called “liners”) made of optimal materials and shaped for friction-fit into cylinder bores of cylinder blocks of internal combustion engines. By using inserts, the cylinder blocks can be made of optimal materials (e.g. low-cost materials that are easily machinable and have high heat transfer properties), and yet the cylinder bores can also be made of optimal materials that will last a long time (e.g. higher cost materials having longer wear and better bearing properties). It is further desirable to minimize the cost of installation of such sleeve-type inserts. For example, most sleeve-type inserts that are friction- or interference-fit into position have a protruding end that must be trimmed after installation. It is desirable to provide an installation and trimming operation that can be done without the need for an expensive milling machine for trimming. This applies to original equipment manufacturers, such as large automotive companies, and also applies to job shops and smaller companies, such as re-manufacturers and engine rebuilders. A problem is that it is difficult to control quality when trying to accomplish machining and trimming operations via manually-operated methods. Fixtures can help, but they are often expensive to build and maintain. Further, they are often cumbersome to use and it is often non-intuitive or unclear how to set up and use them. Notably, even though a manually-operated arrangement is desired, it is also necessary that the arrangement be efficient and quick and that the trimming device be flexible and reliable. For example, the tool must be able to reliably and accurately trim a protruding end of a newly-installed bore insert without leading to damage to the end of the insert and without damage to the engine from loose shavings and debris from the trimming operation.
Another problem with trimming inserts is that the trimmed chips can fall into the cylinder bore. If not removed, they can score and damage the cylinder wall surface, causing considerable damage and thus requiring a second major engine overhaul. Small chips can be especially problematic, since they wedge between the piston and the cylinder wall, where they are engaged and are scraped back and forth with the piston rings. However, removal of all chips is tedious and difficult, especially when the engine block is still in the vehicle where lighting is poor and access is difficult.
Yet another problem with trimmed inserts is their top surface, which must be trimmed flush with a top surface of the cylinder block, so that the head gasket can seal properly between the cylinder block and the cylinder head to prevent oil and radiator fluid cross-contamination and leakage to the cylinder bores. It has been found that the cutters on milling machines, which cutters are rotated as they move linearly across a cutting area, leave a non-cylindrical crisscross pattern on the top surface of the trimmed inserts. This crisscross pattern includes small grooves that lead from the inner surface of the insert (i.e. the cylinder bore) to the outer surface of the insert (i.e. to the top surface of the cylinder block). These small grooves form passages that allow pressurized exhaust gases to sneak under the gasket and over the top of the insert to a remote location adjacent the gasket. Over time, the exhaust gases can enlarge the small grooves, causing premature failure of the gasket, premature loss of compression and engine failure, and other problems. It is desirable to provide an insert trimming apparatus that does not leave a crisscross pattern of grooves on the trimmed end of a cylinder bore insert, to improve the ability to seal a trimmed end of the insert.
Accordingly, a trimming apparatus is desired solving the aforementioned problems and having the aforementioned advantages.